#define _CRT_SECURE_NO_WARNINGS 1
#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int i = 0;
	double sum = 0;
	double c = -1;
	for (i = 1; i <= 100; i++)
	{
		c = -c;
		double ret = 1;
		ret = ret * (c / i);
		sum += ret;
	}
	printf("%lf\n", sum);
	return 0;
}